<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="./js/vue-2.4.0.js"></script>
    <script src="./js/vue-router-3.0.1.js"></script>
</head>
<body>
    <div id="app">
   <input type="text" v-model="plus">+
   <input type="text" v-model="pluss">=
   <input type="text" v-model="equal">


    </div>
</body>
<script>
var vue = new Vue({
    el:'#app',
    data:{
        plus:'',
        pluss:''
    },
    computed:{
        'equal':function(){
           return this.plus + '-' + this.pluss
        }
    }
})


</script>
</html>